This Roman rite seems to have been something different than the modern Wiccan rituals using the term, "Drawing down the Moon."
In Wicca, Drawing Down the Moon is often part of invoking the moon goddess during an esbat. One of the best descriptions can be found in Janet & Stewart Farrar's excellent book, A Witches' Bible, The Complete Witches' Handbook, Phoenix Publishing, Inc., copyright 1981, 1984, from the edition printed 1996, pp. 40, 41, 42. A Witches' Bible, The Complete Witches' Handbook combines two of their earlier books, Eight Sabbats for Witches, 1981, and The Witches Way, 1984. I included a portion of Drawing Down the Moon in the Farrar-Alexandrian Invocation of Aradia. In that section, I summarized the directions of the ritual in order to highlight the wording of a traditional Wiccan invocation of Aradia.
In the Drawing Down the Moon ceremony described in Janet and Stewart's materials, an important point ritual gesture involves the high priest touching the right breast, left breast, and womb on the high priestess several times. In touching these three places, the high priest marks the points of a triangle upon the body of the high priestess to aid in invoking the Goddess into the high priestess. Gavin Bone, who joined the Farrar writing team in 1993, explained in a private correspondence to Myth Woodling:
The triangle is the "invocation of water"--hence upside-down triangle. The idea is that water is receptive and feminine; that the priestess is therefore the receptacle to hold the Goddess energy, i.e. the physical embodiment of the chalice.Water is one of the four elements, or essences--Air, Fire, Water, Earth--which are invoked while creating sacred space. Gavin Bone was specifically referring to the inverted triangle, which is the elemental symbol of water. The physical symbol of water on the altar is the chalice or cup, which is also the symbol of the Goddess. Indeed, an inverted triangle resembles a cup. In other words, when a point-down triangle is traced upon the high priestess, she becomes a vessel for the Goddess to enter like water filling a cup.
(Gavin Bone, November 26, 2005)
For an in depth look at the Drawing Down the Moon ritual, either read Janet & Stewart Farrar's book or visit the website of Janet Farrar and Gavin Bone. The entire ritual can be found in their Book of Shadows, under Drawing Down the Moon, along with casting the circle, calling the quarters, etc.
Solitary Drawing Down the Moon
Farrar-Alexandrian Invocation of Aradia